The singlet-doublet dark matter model offers a rich framework for exploring the nature of dark matter (DM) through its unique fermion structure. In this model, the important parameters are singlet-doublet mass splitting $\Delta{ M}$, singlet-doublet mixing angle $\sin\theta$, and DM mass $M_{ \rm DM}$. If the DM is assumed to be of Dirac nature, then the annihilation, co-annihilation, and conversion driven processes combinedly allows a range of parameter space: $1~{ \rm GeV} \lesssim M_{ \rm DM}\lesssim750$ GeV and $10^{ -6}\lesssim\sin\theta\lesssim0.04$ for all $\Delta{ M}>1$ GeV. While the nature of DM either Dirac or Majorana is not known, in this work we assume the nature of singlet-doublet DM to be of Majorana type and find that the relic density and direct detection can be satisfied in a larger parameter space. In particular, the allowed ranges of DM mass and $\sin\theta$ are: $1~{ \rm GeV}\lesssim M_{ \rm DM}\lesssim1750$ GeV and $2\times10^{ -7}\lesssim\sin\theta\lesssim0.16$ for all $\Delta{ M}>1$ GeV.
Categories: hep-ph astro-ph.CO hep-ex